Field of the Invention
The invention relates to injection devices, and more particularly, relates to methods and devices for detecting a dose of medicament selected on an injection device. More particularly, the invention relates to methods and devices that measure motion or vibration of an injection device to determine what dose of medicament has been selected for injection by a user.
Description of the Related Art
Injection devices are medical devices that allow patients to self-administer their medications outside a hospital or physician's office. These devices are often used for the management of chronic diseases. A typical injection device has a prefilled syringe in a mechanical device that deploys a needle and delivers a medicament with a single push of a release button. The user of a typical injection device is able to select the amount of medicament to be delivered. Injection devices may also be disposable, and can include safety mechanisms to shield the needle both before and after injection.
In order to manage the chronic disease effectively, self-administering patients maintain a log or history of numerous aspects of their daily lives. As part of the log, patients are expected to memorize and record the amount of medicament and the time of each injection, along with eating habits and exercise routines. A missing or erroneous record in the log may create result in incorrect injection information being stored. This can lead the patient to mis-administer future doses of their medicine along with leading medical personnel to make improper decisions with respect to future medication regimens.
To overcome some of these disadvantages, prior injection devices have included optical, capacitive, magnetic or similar methods to detect how much medicine has been injected by the patient. However, these prior approaches result in devices that are large in size, rendering the device bulky and ergonomically unattractive. Some prior injection devices were also designed in a way that affected how the user interacted with the injection device, for example, by introducing a new dose dialing button not originally designed for the injection device. Other prior injection devices detect the dose based on determining the position of a stopper inside the pre-filled cartridge before and after injecting medicament. However, these methods did not provide an ability to determine the direction of or the number of multiple individual dosing events that occur between measurements.